The primary objective of this study is to evaluate the degree of variability in retinal measurements of lutein, a carotenoid macular pigment of human retina, with a new and novel technique of resonant Raman scattering spectroscopy. This technique is generally more objective than psychophysical techniques used for lutein measurements, such as heterochromatic flicker photometry. The technique is non-invasive, and the levels of ocular exposure to argon laser light with the Raman device are well below the safety limits specified by American National Standards Institute regulations. Twenty normal volunteers with normal visual function will be enrolled and the reproducibility of the resonant Raman scattering spectroscopy will be evaluated.